This invention relates to an elastomeric mounting and in particular, although not exclusively, to a mounting intended normally to be loaded in compression and to resist subjecting the elastomeric material to tensile loading.
The invention relates additionally, but not exclusively, to an elastomeric mounting suitable for use in a vehicle suspension such as the suspension of an off-road truck to transmit compression and tensile forces between two relatively movable components, especially between an axle and the end of a bogie pivot beam.
One example of an elastomeric element normally loaded in compression and resistant to tensile loading of the elastomeric material is that described in the specification of U.S. Pat. No. 4,615,513. That comprises an elastomeric body located between and bonded to rigid end plates. The elastomeric body incorporates a plurality of parallel, spaced, flat metal rings to prevent circumferential outwards bulging of the elastomeric body when the end plates are pressed together. The end plates are also held together by means of a mechanical connecting means in the form of holders which extend into the rubber body from the central portion of the respective end plates, and secondly a link element linked to the holders.
In this construction the mechanical connecting means should provide a limitation to the maximum expansion of the elastomeric body, so as to prevent that body being subjected to tensile loading and a risk of tearing. In practice, when subjected to heavy duty use and the high shock loads experienced in use as part of the suspension of an off-road truck, it is found that the chain links and holders can deform and that the elastomeric material becomes torn.
One object of the present invention, but not the exclusive object, is to provide an improved elastomeric mounting in which there is a better ability to withstand shock tensile loading and/or resist subjecting the elastomeric material to tensile load.
In accordance with one aspect of the present invention an elastomeric mounting comprises two rigid end members maintained spaced apart by an intervening tubular body of elastomeric material which defines a central chamber, a connecting means arranged to extend through said central chamber to interconnect said end members and serve at least to resist more than a predetermined separation of the end members, and buffer means provided to act in series with the connecting means at a position between said connecting means and one of the rigid end members thereby to cushion the transmission of force between the end members when the connecting means is loaded in tension.
The buffer means may be a buffer member which comprises an element of elastomeric material. That element may be of a frusto-conical shape. It may be orientated to lie within the axial length of the elastomeric body and to reduce in diameter, or cross-section, with increasing distance from an end of the element closest to a rigid end member of the mounting.
The buffer means may comprise a first rigid buffer member which lies radially within the elastomeric element, e.g. an element of frusto-conical shape, and said first rigid buffer means may provide support or support and location for an end of the connecting means.
The first rigid buffer member may be adapted to prevent or restrain relative rotation between that member and an end of the connecting means.
The connecting means may comprise a chain link, which may be a half link, arranged to seat in a groove or like recess provided in said first rigid buffer member.
The connecting means arranged in series with the buffer means may be of an inextensible kind. It may be of a kind as described in our co-pending UK patent Application of even date and entitled xe2x80x9cElastomeric Mounting (A)xe2x80x9d.
The buffer means may comprise a frusto-conical elastomeric element supported at a radially outer surface by a rigid frusto conical support surface associated, and optionally integral, with a rigid end member. That support surface may be provided by an end member extension of annular shape and which lies interposed between the elastomeric buffer element and an end region of the tubular body of elastomeric material.
The buffer means may lie wholly within the axial length of the assembly of rigid end members and intervening tubular body of elastomeric material.
The tubular body of elastomeric material may be reinforced by rigid, e.g. metal, interleaves embedded therein. At least some of said interleaves may be axially aligned with the axial extent of the buffer means. If the buffer means comprises a frusto-conical shape rigid member between the tubular body and an elastomeric element of the buffer means, it is taught that preferably the inner diameters of said aligned interleaves are staggered in a manner which reflects the angle of inclination of said rigid frusto-conical section. Preferably, as considered in longitudinal cross-section, if the tubular elastomeric body has a surface region which lies at an angle A where it contacts a frusto-conical surface associated with the buffer means, a line connecting the inner edges of said axially aligned interleaves also has an inclination A, but in an opposite direction so as to mirror image the inclination of the frusto-conical surface of the body. It is believed that this advantageously minimises or reduces the stress concentrations that otherwise might arise during compressive loading.
An elastomeric mounting the subject of the present invention may incorporate one or more other features such as are described in detail below, and also one or more of the features as disclosed more generally in any one or more of our co-pending UK patent applications of even date and entitled xe2x80x9cElastomeric Mounting (C)xe2x80x9d and xe2x80x9cElastomeric Mounting (D)xe2x80x9d.